How can I fix this?
following the example below
<telerik:RadScriptManager ID="RadScriptManager" runat="server">
</telerik:RadScriptManager>
<telerik:RadTabStrip ID="RadTabStrip1" runat="server" Skin="Web20" MultiPageID="RadMultiPage1"
SelectedIndex="0" Align="Justify" ReorderTabsOnSelect="true" Width="347px" >
<Tabs>
<telerik:RadTab Text="1">
</telerik:RadTab>
<telerik:RadTab Text="2">
</telerik:RadTab>
</Tabs>
</telerik:RadTabStrip>
<telerik:RadMultiPage ID="RadMultiPage1" runat="server" SelectedIndex="0"
Width="345px">
<telerik:RadPageView ID="RadPageView1" runat="server">
<telerik:RadGrid ID="RadGrid3" Width="750px" DataSourceID="SqlDataSource1" GridLines="None"
runat="server">
<ClientSettings>
<Scrolling AllowScroll="True" UseStaticHeaders="True" SaveScrollPosition="true" FrozenColumnsCount="1">
</Scrolling>
</ClientSettings>
<SortingSettings SortedBackColor="BurlyWood" />
<MasterTableView TableLayout="Auto" />
<HeaderStyle Width="200px" />
</telerik:RadGrid>
</telerik:RadPageView>
<telerik:RadPageView ID="RadPageView2" runat="server">
<telerik:RadGrid ID="RadGrid2" Width="750px" DataSourceID="SqlDataSource1" GridLines="None"
runat="server">
<ClientSettings>
<Scrolling AllowScroll="True" UseStaticHeaders="True" SaveScrollPosition="true" FrozenColumnsCount="1">
</Scrolling>
</ClientSettings>
<SortingSettings SortedBackColor="BurlyWood" />
<MasterTableView TableLayout="Auto" />
<HeaderStyle Width="200px" />
</telerik:RadGrid>
</telerik:RadPageView>
</telerik:RadMultiPage>
<asp:SqlDataSource ID="SqlDataSource1"
runat="server"
ConnectionString="<%$ ConnectionStrings:NorthwindConnectionString_Teste %>"
SelectCommand="SELECT * FROM Customers"></asp:SqlDataSource>
Flavio Lepka